The routine that does the wildbattles is in 0x08082AEC, but only creates 1 pokemon. To change that, we must do a copy of the routine at 0x080829FC, which is the one who creates the pokemon at enemy slot 1. If we could create a hack that asked the game to create a pokemon in the next slot, we could even have 6 wild pokemons at once. I think it would'n be hard to do it.
I already did that. I got the game to generate 2 wild pokémon, and yes, it could easily generate 6. The game would hang badly though, and there is no code in the game for triple battles, never mind sextuple battles.
The bigger issues are the music playing the "you won" music at the wrong point, and the ability/lack of ability to catch the Pokémon on screen.
Once we deal with these issues, and deal with the lack of ability to run from the battle. We'll be in a good position to start implementing this hack into actual hacks.